fix: sync restored previews and unblock nested dialogs

[enderchen]

Restoring a historical version now refreshes the preview, source text, editor state and ZIP file tree together, so editing immediately after restoration cannot save stale content. Preview-page version uploads use the same refresh path, and failed content reads keep editing disabled.

Generic confirmations and prompts now appear above their parent modals, allowing category creation and share-link regeneration to complete with the mouse. Tab/Escape handling and focus restoration preserve the parent modal's interaction state. Market entry points remain hidden as intended for this release.

Validation on the latest main baseline:

• 435 unit and integration tests passed; no failures or skips.
• ESLint and the production build passed.
• 20/20 isolated Chromium workbench regressions passed, including restoration followed by editing, version uploads, ZIP restoration, slow/failed reads, nested dialog confirmation/cancellation, keyboard focus and mobile layouts.
• The full local non-market browser verification passed 72/72 checks.